Canines offer compulsive clues.

People diagnosed wit obsessive-compulsive disorder (OCD) may wash their hands for hours to get rid of imagined impurities. Dogs suffering from canine acral lick dermatitis (ALD) constantly lick, scratch, or bite their paws or flanks, creating sores and sometimes requiring surgery or steroid injections.

Researchers now report tha ALD -- which occurs mainly in large dogs, such as Labrador retrievers -- may represent an animal model of OCD with which to test new drug treatments. Certain drugs that increase the availability of the chemical messenger serotonin in the brain ease the symptoms of OCD and ALD equally well in similar doses over the same time period, reports a team led by psychiatrist Judith L. Rapoport of the National Institute of Mental Health in Bethesda, Md.

In three 11-week trials with 37 dogs exhibiting ALD, the serotonin-enhancing drugs clomipramine, fluoxetine (Prozac), and sertraline markedly reduced licking, whereas placebo pills and a drug that influences another chemical messenger proved ineffective, the scientists assert in the July ARCHIVES OF GENERAL PSYCHIATRY.

To look for anatomical abnormalities that might link the canine disorder to OCD, Rapoport's team has started a brain bank for dogs that displayed ALD during their lives.